How to play a video automatically in a slide in MS powerpoint?

I am using Microsoft PowerPoint 2007 and I am having a problem in playing videos properly through it.
When I present, the only time I could play the video is after I clicked on the slides before and after the slide where the video is inserted. Doing this does not exactly impress the audience.
I really need help on how to work my PowerPoint properly so I wouldn’t have to click back and forth before I could play my videos the next time I do a presentation.
I hope you can help me. Thank you.
